U.S. patent number 4,474,015 [Application Number 06/435,306] was granted by the patent office on 1984-10-02 for method of and apparatus for the controlled cooling of a product.
This patent grant is currently assigned to Planer Products Limited. Invention is credited to Michael J. Christmas, Brian M. Palmer.
United States Patent |
4,474,015 |
Christmas , et al. |
October 2, 1984 |
Method of and apparatus for the controlled cooling of a product
Abstract
For the controlled cooling of specimens which are at least
partially of liquid form, especially biological specimens, it is
important that crystallization at the freezing point takes place
locally, without supercooling, and preferably with absorption of
the latent heat of fusion. At a temperature which is a
predetermined amount above a given critical temperature for the
specimen, e.g. its freezing point, a Peltier effect module is
energized to effect supplementary cooling at a local area, for
example one end of the specimen. The Peltier effect module and the
specimen in its container supported in a sample holder are
relatively movable. Preferably, the module is displaced, this being
initiated by the insertion and removal of the sample holder,
preferably by direct mechanical engagement.
Inventors: |
Christmas; Michael J.
(Worcester Park, GB2), Palmer; Brian M. (Farnborough,
GB2) |
Assignee: |
Planer Products Limited
(Sunbury-on-Thames, GB2)
|
Family
ID: |
27190438 |
Appl.
No.: |
06/435,306 |
Filed: |
October 19, 1982 |
Current U.S.
Class: |
62/3.2 |
Current CPC
Class: |
A01N
1/00 (20130101); A01N 1/02 (20130101); A01N
1/0252 (20130101); B01L 7/00 (20130101); G05D
23/20 (20130101); G01N 1/42 (20130101); G05D
23/1919 (20130101); F25B 21/02 (20130101); F25B
2321/021 (20130101) |
Current International
Class: |
A01N
1/00 (20060101); A01N 1/02 (20060101); B01L
7/00 (20060101); G01N 1/42 (20060101); F25B
21/02 (20060101); G05D 23/19 (20060101); G05D
23/20 (20060101); F25B 021/02 () |
Field of
Search: |
;62/3,467,62,328,448 |
Foreign Patent Documents
|
|
|
|
|
|
|
978441 |
|
Dec 1964 |
|
GB |
|
1023597 |
|
Mar 1966 |
|
GB |
|
Primary Examiner: King; Lloyd L.
Attorney, Agent or Firm: Young & Thompson
Claims
We claim:
1. Cooling apparatus for modifying the cooling rate of a sample
which is at least partially of liquid form, comprising means
defining a working chamber, a sample holder adapted to carry a
sample and insertable into and removable from said working chamber,
locating means positioning the holder at a predetermined position
in the chamber, cooling means within said working chamber adapted
to be connected to an electric power source and to function in
accordance with the Peltier effect to provide a surface at which
heat is absorbed thereby to cool said surface, and means within the
working chamber to effect movement of at least one of said cooling
means and said sample holder in a direction to bring said surface
of the cooling means into thermal contact with only a localized
portion of the sample.
2. Cooling apparatus in accordance with claim 1, including pivot
means on which the cooling means is pivotable toward and away from
said sample, the sample holder being movable in a substantially
straight path toward said predetermined position.
3. Cooling apparatus in accordance with claim 1, which includes
means to displace said cooling means between a first position in
which said surface is in thermal contact with said sample and a
second position in which said surface is remote from said sample,
and means responsive to movement of said sample into said
predetermined position for localized cooling to initiate the
displacement of said cooling means from its said second position to
its said first position.
4. Cooling apparatus in accordance with claim 3, which includes an
abutment surface on the cooling means, the initiation of the
displacement of said cooling means toward its said first position
being effected by the sample holder striking against said abutment
surface.
5. Cooling apparatus in accordance with claim 3, which includes
pivot means on which the cooling means is pivotable for
displacement between its said first and second positions.
6. Cooling apparatus in accordance with claim 5, in which said
cooling means comprises a Peltier effect module and cantilever
support means on which the module is mounted, whereby the cooling
means automatically moves to its said second position when the
sample holder is removed.
7. Cooling apparatus in accordance with claim 1, in which the
cooling means comprises a Peltier effect module and a
heat-conductive element in contact with the module and defining
said surface.
8. Cooling apparatus in accordance with claim 1, in which the
sample holder comprises an elongated rod with carrier means thereon
to support and locate a sample container, said carrier means being
engageable with a projecting portion of said cooling means to
initiate displacement of the latter.
9. Cooling apparatus in accordance with claim 1, which includes
stationary abutment means within the working chamber, the sample
holder comprising an elongated rod having a curved lower end which
is slidingly engageable with said abutment means to steer the
sample holder into a path in which it engages the cooling means to
initiate displacement of the latter.
Description
BACKGROUND OF THE INVENTION
This invention relates to methods of and apparatus for the
controlled cooling of a product. The invention is particularly
concerned with the controlled cooling of specimens which are at
least partially in liquid form. One particular application of the
invention is to the freezing, e.g. for preservation, of biological
materials.
Reference is made to the co-pending U.S. Pat. application Ser. No.
435,308 in the name of M. J. Christmas filed on even date herewith
and which describes and claims various features described
hereinafter.
It is well known to freeze biological and other materials, e.g.
animal embryos, blood constituents etc., for the purpose of
preservation in carrier media. The material is frozen in a liquid
carrier medium at an accurately controlled rate, for example by the
release of liquid nitrogen or some other coolant which is
evaporated in the vicinity of the specimen. Suitable control
equipment is used in the admittance of the coolant to maintain the
appropriate cooling rate. When biological material is cooled, the
critical rate, for instance typically -1.degree. C. per minute is
commenced above the freezing point of the solution/suspension. One
difficulty encountered in such controlled freezing procedures, for
example in the freezing of embryos in liquid nitrogen, results from
the sudden crystallisation of constituents of the material to be
frozen, for example at temperatures between -7.degree. C. and
-16.degree. C. Experience has shown that without special
precautions crystallization during cooling takes place effectively
simultaneously throughout the body of the specimen, with the
resulting "shock" causing damage to the biological material. For
this reason it is common practice in such cases to induce
crystallization at the upper end of the ampoule or other container
for the specimen, by physically contacting the ampoule or container
with tongs or some other metal member which has previously been
cooled in liquid nitrogen. The local crystallization which is
thereby initiated then spreads progressively downwards through the
ampoule or container and throughout the body of the specimen.
Because this crystallization is more progressive, the survival rate
of the biological material is substantially enhanced.
Another problem encountered in such controlled freezing procedures,
and this is not limited to biological specimens, is that when
crystallisation occurs the latent heat of fusion of the
solution/suspension is released and the temperature of the liquid
rises. There is also the potential problem of supercooling of the
liquid, again with the danger of instant massive crystallization
throughout the body of the liquid.
Among the disadvantages of the known methods described above,
particularly the use of metal tongs, is the necessity of
introducing mechanical movement within the cooling chamber, or in
some cases momentary withdrawal of the specimen container, thus
creating a risk of upsetting the control of the cooling rate. In
addition, such manoeuvres are extremely inconvenient to the
operator and require skill and expertise in order to achieve
consistent satisfactory results.
It is an object of the present invention to provide apparatus for
modifying the cooling rate of a specimen which is at least
partially in the liquid phase, in a controlled manner. This may be
for example to induce crystallisation of the body of liquid at a
particular location, or to induce precipitation or sedimentation of
material from the liquid, or to absorb the heat of an exothermic
reaction.
It is an object of a preferred embodiment of the present invention
to provide an improved apparatus for at least partially removing
the latent heat of crystallisation of a liquid which is
progressively cooled, thereby considerably reducing the temperature
rise within the liquid resulting from the latent heat of
crystallisation.
Such preferred absorption of the latent heat of crystallisation or
fusion is effected either automatically or under manual control
without any need for mechanical movement of the specimen or the
introduction of a foreign body, such as a pair of cold tongs.
In accordance with the present invention there is provided a
cooling device for modifying the cooling rate of a specimen which
is at least partially of liquid form, comprising cooling means
arranged to be connected to an electric power source and to
function in accordance with the Peltier effect to provide a surface
at which heat is absorbed thereby to cool said surface, and a
sample holder arranged to carry a specimen, wherein the cooling
means and the sample holder are relatively movable to bring said
surface of the cooling means into thermal contact with the
specimen.
Preferably, there is provided means to displace said cooling means
between a first position in which said surface is in thermal
contact with said specimen and a second position in which said
surface is remote from said specimen, wherein the displacement of
said specimen into a position for cooling initiates the
displacement of said cooling means from its said second position to
its said first position.
Preferably the initiation of the displacement of said cooling means
towards its said first position is effected by the sample holder
striking against a portion of the cooling means.
Preferably said cooling means comprises a Peltier effect module
mounted on a cantilevered support whereby the cooling means
automatically moves to its said second position when the sample
holder is removed.
In order that the invention may be fully understood various
embodiments in accordance with the invention will now be described
by way of example and with reference to the accompanying drawings,
in which:
FIG. 1 is a schematic representation of a biological freezer
incorporating a working chamber holding a specimen which is
arranged to be cooled in a controlled manner in accordance with the
present invention;
FIG. 2 is a graphical representation showing a typical rise in
temperature which occurs in a liquid when it undergoes
crystallization;
FIG. 3 is a similar graphical representation showing the effect of
the use of the method and apparatus of the present invention in
reducing the rise in temperature within the specimen;
FIGS. 4a and 4b are perspective and side views respectively of a
first embodiment of cooling apparatus in accordance with the
present invention;
FIGS. 5a and 5b are similar perspective and side views of a second
embodiment of cooling device in accordance with the invention;
FIG. 6 is a schematic illustration of an optical device which can
be used in conjunction with the apparatus of the present invention;
and
FIGS. 7a and 7b are side views of a further embodiment of cooling
device in accordance with the invention.
The embodiments illustrated in FIGS. 1 to 6 are described also in
the aforesaid co-pending U.S. patent application Ser. No. 435,308
in the name of M. J. Christmas entitled "Method of and apparatus
for the controlled cooling of a product" filed on even date
herewith.
Referring first to FIG. 1, this shows a freezer 10, for example a
conventional biological freezer, which incorporates a working
chamber indicated generally at 12. Also provided is a
programmer-controller unit 14 which is effective to control the
temperature/time profile of the cooling process which takes place
within the working chamber 12. For this purpose the
programmer/controller unit 14 is connected to a temperature sensor
16, mounted within the working chamber. Connected to the working
chamber 12 is a coolant supply pipe 18 which incorporates
appropriate control valve means 20. This control valve means 20 is
connected to the programmer/controller unit 14. An output pipe 22
is also connected to the working chamber 12. The freezer 10 is a
conventional unit and the other component parts, mechanical,
electrical and/or electronic, will not therefore be described in
detail.
Within the working chamber 12 there is mounted a sample 24. This
sample 24 contains the liquid or liquid and solid which is to be
treated, for example frozen, and may comprise for example a glass
ampoule, a bag or other container, a thick-walled plastics
container, a plastics straw, or a metal container. It should be
understood that the present invention is appropriate for use with a
sample container of any shape or material.
Also mounted within the working chamber 12 is a unit, indicated
generally at 26, which is at the heart of the present invention and
which comprises a Peltier-effect type cooling device. Embodiments
of such a device are shown in FIGS. 4, 5 and 7 and will be
described in more detail later. The Peltier effect is the
phenomenon whereby heat is absorbed, or liberated, at a junction
where an electric current passes from one metal to another.
FIG. 2 illustrates what happens when a liquid, for example a
solution or suspension, is cooled through its freezing point. It
will be seen that as the temperature falls from 0.degree. C. to
-5.degree. C. the cooling curve is linear. At the freezing point,
i.e. -5.degree. C., as crystallization occurs, latent heat is
generated which delays the further cooling of the liquid and
creates an attendant risk of damage to biological specimens. The
latent heat of crystallisation has to be absorbed by the gas around
the sample 24 within the working chamber 12. In contrast, as shown
in FIG. 3, with the method and apparatus of the present invention,
one achieves a quite different rate of cooling curve. The curve
departs only very slightly from the straight lines because of the
much more rapid absorption of the latent heat with the system of
the present invention. As will be explained hereinafter, the method
and apparatus of the present invention provide local cooling for
the sample, either to absorb this latent heat, instead of leaving
this to the environmental gas within the chamber, or to initiate a
boost in the cooling due to the environmental gas in the case where
the local cooling is just used to induce crystal formation.
Referring now to FIGS. 4a and 4b, there is shown therein a first
embodiment of the Peltier-effect type cooling device 26. Two
Peltier-effect modules 28a and 28b are here connected in series to
a suitable dc power supply source (not shown). Although a series
electrical connection is shown, the modules could alternatively be
connected in parallel or in some compound arrangement. Also,
although in this described embodiment a pair of Peltier modules are
used, one could alternatively use just a single such module. Each
module comprises a series of p and n doped, bismuth telluride type
limbs arranged in series so as to create a cold junction and a hot
junction. The "hot" face 30 of each module 28a, 28b is covered with
a suitable heat transfer compound, for example a grease, and a pair
of heat sink plates 32a and 32b are secured respectively on the hot
face of each module. Each of the heat sink plates 32a, 32b is
equipped with fins 34 to enable the heat transferred to the heat
sink plates to be dissipated into the working chamber 12 in such a
way that the temperature/time profile set by the temperature
programmer/controller unit 14 is maintained. The "cold" faces 36 of
the Peltier-effect modules 28a, 28b are also covered with a
suitable heat transfer compound, such as a grease, and a conductive
metal strip or plate 38 is mounted so as to connect these two cold
faces 36. As shown in FIG. 4a, the conductive metal strip 38, which
may be for example of copper, aluminum or some similar high
conductivity material has three separate areas. These consist of a
pair of end plates in contiguous and overlapping relationship with
the respective modules 28a and 28b, and a central bridging strip 40
of reduced width. This bridging strip 40 is provided with one or
more corrugations or indentations 42 which are shaped to
accommodate the sample container 24 with surface-to-surface
contact. The provision of such corrugations 42 allows an increased
surface area contact between the strip 40 and the container 24, and
is particularly suitable for containers 24 having poor thermal
conductivity, for example glass or thick-walled plastics
containers. A spring clip or clamp 44 is provided across the device
to clamp the container or containers 24 on to the conductive strip
40. The distance apart at which the Peltier modules 28a and 28b are
set is determined by the dimensions required to accommodate the
container or containers 24 on the strip 40. Two thermal insulating
plates 46a and 46b are provided on the respective wing portions of
the conductive strip 38 on the faces thereof which are opposite
those faces which are in contact with the modules 28a and 28b.
Although in the preferred embodiment the sample container 24 is in
direct surface-to-surface contact with the conductive strip 38, 40,
one could simply have the container spaced slightly from the strip
or from a "cold" face, thereby maintaining thermal contact but not
necessarily surface contact. Also of course, the sample container
could be horizontal rather than vertical, and simply laid on the
strip or "cold" face.
FIGS. 5a and 5b show a slightly modified arrangement in which the
central bridging portion 40 of the conductive strip 38 is not
indented or corrugated but is flat. This embodiment, where there is
a reduced surface-to-surface contact between the sample container
24 and the bridging portion 40 of the strip 38, is suitable for
containers 24 which have a low thermal mass, for example plastics
straws or metal containers. It will be appreciated that other
configurations of conductive strip can be devised to match the
requirements of particular shapes of container, and particular
container materials.
FIG. 6 shows an optical device which can be used in conjunction
with the controlled cooling device of the present invention to
detect the phase change from the liquid state to the crystalline
state. A light beam from a light source 50 is transmitted through
the sample container 24 towards a receiver 52. When the sample
within the container 24 is in the liquid state the light beam will
be detected by the receiver 52, but when there is a change to the
crystalline state upon freezing, or upon the creation of a
precipitate or sediment within the container, the light beam will
be attenuated or completely blocked and the receiver 52 will detect
this change. This detector can be linked up to the
programmer/controller unit 14 so that the additional cooling
introduced by the Peltier modules 26 is immobilised as soon as
crystallization, precipitation or sedimentation has taken place.
The term "light beam" used in relation to FIG. 6 is intended to
include not only visible light but also other electromagnetic
radiation which can be transmitted in the form of a beam. Again,
other types of sensor than optical sensors could be used to detect
the aforesaid phase change.
One preferred method of operation of the apparatus as hereinbefore
described will now be given. The apparatus is set up with a
specimen in a sample container 24 clamped to the conductive strip
38, 40. The Peltier assembly is mounted in the working chamber 12
of the freezer 10. A coolant, such as liquid nitrogen, is passed
into the working chamber 12 through the inlet 18 to cause cooling
of the specimen and container 24. Preferably, the sample container
24 is mounted so that one end of the container is in contact with
the bridging portion 40 of the conductive strip, so that the local
cooling effected by the strip is effected at one end of the
container. Particularly when freezing biological specimens, it is
desirable to initiate crystallization from one end of the
container, preferably the upper end. Additionally, the Peltier
assembly is spring-loaded within the cooling chamber to engage with
the sample container 24 throughout the cooling process.
The degree of heat conduction between the sample container 24 and
the strip 38, 40 is preferably first determined by initial
experimentation, together with the measurement of the freezing
point. Having thus determined the parameters of the particular
system, the system can be set up for initiation of the local
cooling by way of the Peltier device at preferably less than about
2.degree. C. above the determined freezing point of the sample. The
intention is to absorb heat locally around the upper surface of the
liquid in the container 24 in order locally to induce seed crystals
within the liquid. By matching the thermal masses of the cooling
device and of the container 24 it is possible to achieve a
carefully controlled initiation of these seed crystals. Preferably,
the programmer/controller unit 14 (FIG. 1) is connected to the
Peltier module 26 by a lead 54 and produces separate signal outputs
at predetermined temperatures which are passed to the Peltier
device 26 so that the Peltier device is actuated at a precise
predetermined temperature.
When the temperature of the sample within the container 24 is close
to the freezing point, an electric current is passed through the
Peltier device, resulting in the cold faces 36 becoming colder and
lowering the temperature of the conductive strip 38, 40. An
electric current of for example 0.5 amps at 12 volts may in
practice be passed through the Peltier modules when the specimen
has reached the determined temperature just above the critical
crystallisation, precipitation or sedimentation point. The current
is maintained for a period of for example 10 seconds in order to
produce the necessary local cooling which will induce
crystallization, precipitation or sedimentation at that part of the
container which is in surface-to-surface contact with the strip 40.
This crystallization, precipitation or sedimentation will then
spread progresssively through the whole of the specimen as the
temperature continues to fall due to the continuing presence of the
surrounding coolant, whether boosted or not.
If an optical device as shown in FIG. 6 is used, then this will
detect the phase change from the liquid state to the crystalline
state in that part of the sample container wherein local cooling is
initiated, and can be used to trigger the programmer/controller
unit 14, for example to effect termination of the additional
cooling by way of the Peltier device as soon as the local
crystallization, precipitation or sedimentation is detected.
It will be appreciated that no mechanical movement is required to
initiate the local cooling of the sample, and there is no need for
the operator to interfere with the sample container itself during
the cooling process. With the use of a microprocessor-type control
unit as the programmer/controller unit 14, it is possible to
programme this in such a way as to operate the Peltier device at a
given preset temperature.
It is also advantageous to provide for vibration of the specimen
during the cooling process. This can be achieved by mounting the
whole assembly 24, 26 on a suitable vibrator mounted either outside
or within the working chamber 12. The vibration of the specimen
within the container 24 during the cooling process reduces the
chance of local supercooling of the sample. This also makes it
easier to predict the crystallisation point.
In the embodiments of cooling device described above the sample
containers 24 are either clipped to the Peltier modules or are held
clamped against them, and the Peltier modules themselves are
mounted in a fixed position. FIGS. 7a and 7b show an alternative
embodiment of cooling device in accordance with the invention which
is particularly useful for partial automation of the cooling cycles
and procedures with which the present invention is particularly
concerned. In this embodiment the Peltier module is not fixed, but
is movable, and indeed movable in response to the presence or
absence or a sample container. As will be explained in more detail,
by the insertion of a sample container into the cooling device, the
Peltier module is automatically brought into the current position
for intimate contact with the sample container at the correct point
in order to facilitate the desired shortterm supplementary
cooling.
FIG. 7a shows the situation where a sample container in the form of
an ampoule is about to be lowered into a working chamber which
contains the Peltier module, and FIG. 7b shows the relative
positions of the components after the ampoule has been lowered into
the housing into thermal contact with the Peltier module.
As will be appreciated, in this embodiment, a single Peltier module
is used, as compared with the use of a double module in the earlier
embodiments. However, the device illustrated in FIGS. 7a and 7b is
particularly appropriate for use when one has a working chamber
adapted to receive a plurality of sample containers, and where one
would then have a number of such Peltier modules mounted in rows or
lines, or in some other array, within the working chamber, with
each position receiving a respective one of the sample containers.
One is thus able to effect the appropriate cooling of a number of
samples under the same conditions and at the same time.
As shown in FIGS. 7a and 7b, the sample container 24, here shown as
an ampoule, although it could be a straw or other container, is
arranged to be carried in a bucket 60 secured to or integral with
ampoule holder 62 in the form of an elongate rod having a curved
lower end 64. The upper end of the ampoule holder 62 is provided
with a cylindrical plug 66 sized to fit into a hole 68 through the
top wall 70 of the working chamber, and with a cylindrical cap 72
by means of which the holder assembly can be grasped.
The Peltier module 28 is provided, as in the preceding embodiments,
with cooling fins 34 and is mounted on a cranked support member 74.
The support member 74 is pivotally mounted by a hinge member
indicated at 76 and has a bottom surface 78 which, in the attitude
shown in FIG. 7b, approaches a stationary stop 80. A further stop
82 is provided, against which the support member 74 rests when the
assembly is in the position shown in FIG. 7a. A rod 84 which is
secured to or is integral with the support member 74 projects
forwardly from the support member and is arranged to extend
horizontally when the assembly is in the position shown in FIG. 7b.
The "cold" face of the Peltier module 28 has a yoke 86 fixed to it,
for example by soldering. The yoke 86 is of a material which is an
extremely good conductor of heat, and is preferably of copper. The
yoke 86 is shaped so that it has a reducing cross-sectional area in
the direction away from the face of the Peltier module, and the
face of the yoke adjacent to the ampoule is suitably shaped so that
it can make intimate contact with the ampoule. Thus, this face of
the yoke is generally smoothly concave.
Below the Peltier module assembly there is mounted a stationary
receptor 88 which has an upwardly directed hole or slot arranged to
receive the ampoule holder 62 as it is lowered into the working
chamber. The receptor 88 is positioned in relation to the ampoule
holder 62 so that as the curved lower end 64 of the ampoule holder
strikes the edge of the hole or slot in the receptor 88 the ampoule
holder 62 will be "steered" so that the bucket 60 on the ampoule
holder moves laterally towards the Peltier module assembly as the
ampoule holder is lowered into the working chamber. A backing
support 90 in the form of a rod is provided on the ampoule holder
62 at a position where it lies behind the ampoule 24.
In use, when the ampoule holder 62 is not present, or is in its
raised position as shown in FIG. 7a, then the Peltier module
assembly tilts backwards about the pivot 76, into contact with the
stop 82, because of the cantilever effect arising from the Peltier
module being mounted at the upper end of a cranked arm of the
support member 74. When the ampoule holder 62, with an ampoule 24
having its base seated in the bucket 60, is lowered down through
the hole 68 in the top of the working chamber, the curved lower
portion 64 of the ampoule holder first strikes against the edge of
the slot in the receptor 88, and the ampoule holder 62 is
thereafter displaced so that the base of the bucket 60 strikes
against the projecting rod 84 of the support member 74 and tilts
the Peltier module assembly into an upright position, as shown in
FIG. 7b. In this position the yoke 86 presses against the ampoule
24 at the desired position towards the upper end of the ampoule,
and exerts a pressure against the ampoule against the restraining
effect of the support rod 90.
With the components in the position shown in FIG. 7b one can then
commence the cooling process in the manner already described
above.
It will be appreciated that the cooling device as described in the
latter embodiment is particularly attractive when one is
considering semi-automation of the cooling of large numbers of
samples. The ampoules or straws or other containers can be loaded
into the ampoule holders outside the working chamber and, simply by
lowering them into the working chamber, the Peltier module is
brought accurately and reliably into contact with the appropriate
part of the ampoule without manual adjustment and without the need
for clips, springs, etc. It will be appreciated that the mechanical
structure used for accomplishing this technique can be modified
within the scope of the present invention. For example, instead of
using an ampoule holder 62 having a curved lower end, one could use
a straight rigid rod and provide a stationary inclined surface
instead of the receptor 88, whereby the lower end of the rod, in
striking against the sloping surface and sliding down it will again
be displaced towards the Peltier module assembly in order that the
bucket 60 would strike against the projecting rod 84.
A further advantage of the embodiment last described above is that
the sample container, whether it be an ampoule, a straw or
whatever, is reliably held in the correct position so that the
right portion of the sample container is presented for contact by
the yoke attached to the Peltier module itself.
Although the described embodiment shown in FIG. 7 uses direct
mechanical engagement of the sample holder with the cooling
assembly to initiate movement of the cooling assembly, one could
alternatively use an electromechanical system where the insertion
of the sample holder into the working chamber actuates a switch
which triggers a motor to drive the cooling assembly from its
out-of-contact position to its operational position.
It is emphasised that in its broadest aspect the present invention
is concerned with affecting or modifying the rate of cooling of a
specimen. The method and apparatus of the invention are therefore
appropriate also for the absorption of the heat of an exothermic
reaction occurring during a cooling process, even if no
crystallisation, precipitation or sedimentation occurs at that
point in the cooling process.
Additionally, although in the embodiment shown in FIGS. 7a and 7b
the sample holder is movable in a generally straight path, here an
essentially vertical path, and the cooling assembly is pivoted for
pivotal movement, it should be understood that the present
invention is not to be regarded as limited to this particular
arrangement. Other ways of achieving relative movement between the
cooling assembly and the sample holder are to be regarded as
falling within the spirit and scope of the present invention.
* * * * *